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MrSeb writes "Researchers from the University of Oulu in Finland has created an indoor navigation system (IPS) that uses the Earth's innate magnetic field to ascertain your position — just like a homing pigeon or spiny lobster. According to IndoorAtlas, the company spun off by the university to market and sell the tech, its system has an accuracy of between 0.1 and 2 meters. The Finnish IPS technology is ingenious in its simplicity: Basically, every square inch of Earth emits a magnetic field — and this field is then modulated by man-made concrete and steel structures. With a magnetometer (compass), which every modern smartphone has, you can first create a magnetic field map — and then use that map to navigate the shopping mall, underground garage, airport, etc. Compared to most other IPSes, which require thousands of WiFi or Bluetooth base stations to achieve comparable accuracy, IndoorAtlas' infrastructure-free approach sounds rather awesome."

No, thats what I thought but watch the video, they do something much simpler (i.e. have the user directly input where they are going on a map, while taking magnetic measurements on the phone).

Move smartphones have an accelerometer, so it should be possible to build this map by dead reckoning, especially if you can accumulate the data from enough different devices and/or different journeys...

start position = outside where you had GPS signals. Landmarks can be used to correct for drifting. That's how decent navigation software works, Accelerometer corrected with GPS locations when available (which is usually once per second when a signal is available). How else can it work in a tunnel or a bad urban canyon?

"Decent navigation software" just uses your last calculated velocity from your last successful GPS fix to move you along the calculated route. You can demonstrate this yourself by using underground tunnels and intentionally taking the wrong turn or even just slowing down - the GPS doesn't have any fancy accelerometers to notice you've changed course or speed, it continues to show you moving along the calculated route at your old speed, at least until you come back out into the open air to get a new GPS fix.

I assume that nobody here has actually used this system, so surely we can only say that theoretically it is bad in practice. In practice, they may have accounted for these problems in their theory.

My guess is that their software would not assume that people are lurching tens of meters in a single moment just because they pass something magnetic. They would use the same smoothing algorithm that GPS mapping uses. Have you ever noticed when you first load up a map on your GPS position is often quite inaccurate initially before eventually pin-pointing your location a few seconds later. They smooth out any anomalous readings after this, which you can see when your position briefly pauses while you are moving at a constant speed. During those pauses, the system has received new location that differs significantly from the last reading. These are obviously ignored to give the illusion of accuracy.

This magnetic system could do the same. With bidirectional communication, the software could report back anomalies due to changed environments and incorporate them into the self-correcting maps. Given that shopping centers do want to track their shoppers [slashdot.org], it seems quite likely that there would be bidirectional communication happening.

And rife with problems, including transient ones. The earth's magnetic field, while kind of constant at each point, can vary wildly in just a few meters. Most of the earth has lots of iron in it, and it doesn't take much to shift it around to the point where Hall sensors go whack. Nice idea, but in practice it will be really difficult. I'll get a nice hand-wound field coil, put on a randomly generated VCO, and watch their devices implode. Yes, they can degauss your ancient monitor, and wreak havoc on Hall d

the variance in the magnetic field is the POINT here. the are mapping these subtle/dramatic variations, and using them as measurable waypoints for navigation. (ie, there is a lot of magnetic field outside the GAP in this mall, but a lot less in front of the dip'n'dots, and there are a series of spikes by the fountain across from the dillards etc. etc. etc.) yeah, sure you can wipe out the magnetometer with a field coil, or (maybe) make the map return bad results by throwing 50 hard drives in a trash can, b

We agree on the point. My contention: it changes, and therefore the data is a variable. Yes, some places have lovely static fields. You can walk from points a-z and little changes....

Until something changes, and it will. A simple GPS is likely to have more immunity from fluctuations as its point source is an enormous distance away, which is precisely what makes GPS tough to resolve at many thousands of miles. The magneto sensors in a cellphone are going to get Hall Effect distortions pretty regularly, and t

For magnets of reasonable size, even the most powerful ones that you can reasonably buy have a surprisingly small area of noticeable field strength. A rare-earth puck will be good for a bit over a Tesla at the surface, and two of them can make friends with one another hard enough to take your finger off; but would drop into the background surprisingly quickly as you moved further away...

I suspect that once your phone has encountered an MRI, small navigational errors will not be high on your list of concerns... The videos of hardware that can put a 3 Tesla field across an entire patient ingesting ferromagnetic objects are... dramatic.

Basic compass navigation has two data points: North and South. This has millions. It uses a compass, true, but it uses a sophisticated vector map of magnetic fields which normal compass navigation does not.

Yes and no. A compass just gives you your heading, relative to magnetic north. This will presumably be able to do that; but(depending on how much variation is available in the local magnetic field) it may also be able to give you an approximate location by detecting local magnetic anomalies.

The ground-level strength and orientation of the earth's magnetic field varies a bit naturally, for geological reasons, and our dense masses of ferrous structures and AC wiring probably provide a considerable amount o

Some Chinese people will sell you coated iron-foil as aluminum foil, because steel is a few cent cheaper than alumunium. (they already do so for Utp [microtech.net.pk] just test with a magnet if you fail to get gigabit speeds on your network)

I thought that the API for a compass in a smartphone really just supplied a bearing, but I'll assume they are assuming access to the raw data that comes from the hardware.

Still, are these magnetometers anywhere close to sensitive enough? I would think they are built to be as cheap as possible. I would expect them to be only accurate enough to determine which side of the road you're facing. This application must require amazing accuracy. I'd be amazed if they can get it out of a smartphone.

My phone (HTC EVO 3D) has a compass, accelerometer, gyro, and flux sensors. It's sensitive to changes as small as a single microtesla that I can tell, though noise usually means your sample resolution is about 5, instead. Some filtering would probably do nicely, since I'm only able to look at the raw reading.

Bored? Grab your phone and run the app "GPS status" or probably a million similar apps, maybe even some free ones. Then move stuff around on your desk to see how the field changes. I can vary it about 20% by waving my steel clipboard around the phone. Now its possible with enough filtering you can assume changes are solely due to movement rather than me trying to sabotage the data gathering, and perhaps the map is actually of the 1st (or 2nd?) derivative of the field around my desk rather than just mapping the raw data so it doesn't matter if I'm IronMan and you're not, or if our phones do not have absolute calibration.

If I had more time on my hands I'd throw a fridge magnet on the floor, and try to "find the titanic" using the magnetometer and some string and graph paper and walking a grid pattern, or maybe pulling my phone along the floor on the grid pattern. Very much like the movie, I'll probably get bored halfway thru this titanic experiment. But it would probably work. Someone out there in/. land oughta try this, maybe try a big chunk of ferrous metal too, like a manhole cover (try not to get run over...)

it was bad on the nexus s on android 2.3 (?, the one before 4.0). In the compass app i could turn my phone around 180 degrees, and the needle almost followed along , now pointing almost in the opposite direction. I just tried it again now, on 4.0, and the compass works pretty well, it seems to have a precision of a few degrees when rotating the phone. I imagine there's some smart signal processing going on. Btw, I thought the exact same as the parent(and I don't have a good answer, just my experience)

I can't pinpoint it exactly, but the way the phone is being held doesn't seem quite right. Like it was faked or done on a computer. Is this really just a concept video?

The camera is fixed on the phone like they had some kind of brace mounting on his arm. It makes for a steady shot, but it doesn't look natural at all. It looks like a 3D shooter where the view is always centered on the gun.

I also noticed that when focused on the phone, the rest of the world is a blur. I'm not going to enjoy dodging people who are staring down at their phones while walking, completely oblivious to what's going on around them. It would, however, be hilarious to mess with the magnetic field en

To be fair, you can't significantly alter the earth's magnet field with anything particularly portable... while the field strength of the earth's field is quite low compared to what we can generate artificially, the size of the field is so many orders of magnitude larger than anything man-made, that owing to how fast strength drops off with distance, I simply don't think there's too much to worry about with regards to man-made objects changing what the perceived field is unless you are within mere inches o

A "Helmholtz coil", is actually a pair of coils, that will produce a uniform magnetic field in a cylindrical region between the coils. A "Maxwell coil" is a pair of coils wired to produce a cylindrical magnetic field with a linear gradient between the coils.

Make a pair of big coils, put some power through it, and you can make a big electromagnetic field. Depending on how you connect the coils, the magnetic field will have interesting properties. With simple electronics, you can vary the field strength bet

I'll admit i wasn't sure exactly how to make those changes, but it would be hilarious none the less. Probably much easier to just put up a temporary wall that isn't on the phone's map. I'm sure some people would be so focused on starting at their phones that they would walk right into it. For wild animals, natural selection deals with that sort of obliviousness for any species that has predators. Sometimes I worry that technology lets us get away with being more incompetent that we should really be allowed

You're correct. The scene is moving all through the store, but the hand seems locked in in one part of the picture, without any of the normal movement one would expect to see. Even if the camera were shoulder or arm mounted you would see some normal hand movement that is lacking here. This is clearly a mock-up. But that is to be expected when you are trying to sucker investors with a technology that can't really work. And, of course, I mean allegedly trying to sucker investors.

There is just no way that one would get enough information from a magnetometer to give you the information to do this, any more than a compass in the great outdoors can tell you where you are, it can only tell you headings. Of course, there are all of the other issues that people bring up also, like metal or electrical things moving in the area and changing (effectively randomizing) the minimal information that you have. But to focus on that only ignores the greater problem, any simple vector from a magnetometer (even if it included a vector strength) can't tell you a location in 2D or 3D space. And unless you somehow magically know the correct way to orient your magnetometer when you are holding it, then just moving it as you move through the structure could give you any magnetometer direction at any point.

Buildings and other large structures rarely change much. The magnetic field in any particular spot may change due to objects moving about, but that acts as spatial high-frequency noise over a much more stable lower-frequency signal.

The simily is imperfect, but when you compare the map with reality you ignore the small stuff like parked cars, curbside junk, temporary road-works structures and so on and focus on the stable larger-scale structures in the environment. In the same way, this would loook at the la

I understand what you're saying, but I have to disagree because you appear to be quite narrowly stipulating the usage of the technology for the purpose of your analogy.

The magnetic field in any particular spot can change for any number of reasons including, for example, the simple scenario of someone using electrical equipment. Something as simple as an electrical device being plugged into the wall, someone placing a computer based kiosk in the area, a television or monitor being turned on, someone using a

I think the main observation to take is that very rapid, unpredictable changes (a floor polisher, say) also tends to introduce only very _local_ changes. The effects stretch for decimeters, rather than meters, and for seconds or so when the machine is close. A larger, fixed machine that is either on or off, on the other hand, would essentially introduce two alternate local maps, both of which could be estimated and learned.

Remember that these sensors are fairly insensitive to small changes; they

I agree with regards to the size of the changes and the ways they could be overcome; however, that is an academic exercise that assumes many conditions. This is being presented as a consumer technology for mapping interiors for consumption by consumer mobile devices.

Regarding computer visions, I wasn't referring to background learning, I was referring to kernels we use to recognize objects in the scene (speed samples, orientation change rates, sizes in given dimensions against camera orientation,et cetera.)

Reliable indoor positioning is probably one of the key pre-requisites to building workable augmented-reality apps like games and such. There's probably a real payoff for the long term, but maybe not for the group that invents the underlying concepts/tech, unless they find some way to see it through to applications.

Second, and perhaps more importantly, what about the effect of objects that aren’t part of the original magnetic field map, such as cars, moving lifts, and electric motors? Who knows, though — perhaps the effect of these objects is negligible.

well, most everyone knows actually. the effects of even a slab of metal is significant. the effects of powered devices like a monitor, or an electric motor, or a stationary magnet are massive. anyone can see it. grab an app that displays the magnetic levels from your smart phone's sensor, and watch them fluctuate wildly as you move it past various electronic devices.

i guess it's okay though because places like malls aren't known for having electronic devices about... oh wait. maybe they have some great tec

I suppose they modulate the magnetometer with a transphasic ringtone, while diverting power from the non essential functions to the positioning system, and firing a synchronized serie of photon beams trough the back facing camera's LED. To activate, just say: "Engage".